Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 14,553	$ 12,013	$ 53,851	$ 45,351
Other comprehensive income, net of tax:
Change in pension benefits, net of deferred taxes of $(173) and $(138), and $(518) and $(413), for the three and nine months ended January 31, 2017 and 2016, respectively	270	215	810	646
Total Comprehensive Income	$ 14,823	$ 12,228	$ 54,661	$ 45,997